The advent of floating production systems has produced a variety of single-point mooring methods whereby a fixed production riser is connected to a surface vessel. These system require swivel assemblies and the present invention is directed to these assemblies but is not necessarily restricted thereto. The swivel assemblies are required because the riser remains in a fixed position while the vessel is free to rotate due to wind and current effects. The swivel assemblies according to the present invention can be used in conjunction with the apparatus described in copending U.S. patent application Ser. No. 578,204 entitled "Apparatus And Method For Connecting Subsea Production Equipment To A Floating Facility" filed Feb. 7th, 1984.
The existing swivel assembly systems using conventional seals technology have poor reliability and low pressure ratings. The seals rapidly break down because of excellerated wear caused by contaminants in the produced fluid and the effects of dimensional instability. At high pressures, 10,000 psig and above, structural deflection is a major design problem. Seal retaining grooves must remain in close proximity to the sealing surface in order to maintain seal integrity.